Optimization and Analytical Applications of the Technique of Dynamic Introduction of Liquids into Centrifugal Analyzers

The technique of dynamically introducing a measured volume of liquid into the spinning rotor of a miniature Centrifugal Fast Analyzer where it is subsequently apportioned into equal aliquots [C. D. Scott and J. C. Mailen, Clin. Chem. 18, 749 (1972)] has been further developed and improved. Several important structural and operational factors have been identified and investigated, including rotor design and geometry, rotor speed, injection volume and rate, and probe diameter. To determine the effect of these factors on the precision and accuracy with which a liquid may be dynamically introduced and apportioned, we developed a dye-dilution procedure. These studies demonstrate that liquid volumes ranging from 10 to 50 µl per cuvet can be dynamically loaded with an accuracy and precision (expressed as standard deviation) of 1 to 2% and 0.5 to 1.1 µl per cuvet, respectively. Several analytical applications of this technique have been investigated: ( a ) measurement of true sample-blank absorbance before dynamic reagent introduction, ( b ) sequential reagent addition, ( c ) correlation studies involving discrete versus dynamic loading of reagent, and ( d ) reconstitution of lyophilized reagents.